Berlin 2018 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 16: Active Matter II (joint session DY/CPP/BP)

DY 16.1: Talk

Monday, March 12, 2018, 15:30–15:45, BH-N 243

Run-and-Tumble-like Motion of Synthetic Microswimmers in Viscoelastic Media — •Celia Lozano, J. Ruben Gomez-Solano, and Clemens Bechinger — Fachbereich Physik, Universität Konstanz, Konstanz D-78457, Germany

Run-and-tumble (RNT) motion is a prominent locomotion strategy employed by many living microorganisms. It is characterized by straight swimming intervals (runs), which are interrupted by sudden reorientation events (tumbles). In contrast, directional changes of synthetic microswimmers (active particles, APs) are caused by rotational diffusion, which is superimposed with their translational motion and, thus, leads to rather continuous and slow particle reorientations. Here we demonstrate that APs can also perform a swimming motion where translational and orientational changes are disentangled, similar to RNT. In our system, such motion is realized by a viscoelastic solvent and a periodic modulation of the self-propulsion velocity. Experimentally, this is achieved using light-activated Janus colloids, which are illuminated by a time-dependent laser field. We observe a strong enhancement of the effective translational and rotational motion when the modulation time is comparable to the relaxation time of the viscoelastic fluid. Our findings are explained by the relaxation of the elastic stress, which builds up during the self-propulsion, and is suddenly released when the activity is turned off. In addition to a better understanding of active motion in viscoelastic surroundings, our results may suggest novel steering strategies for synthetic microswimmers in complex environments.